There is considerable evidence to suggest that brain dopamine systems are involved in appetitively motivated behavior. DA antagonist drugs impair the performance of behavior maintained by a variety of reinforcers, and reinforcing stimuli have been shown to increase the release of DA in some brain structures. These data often are interpreted as supporting the hypothesis that DA, especially in nucleus accumbens, mediates the rewarding properties of stimuli such as food, water and drugs of abuse. However, evidence also indicates that DA is involved in aversive motivation. Administration of DA antagonists or depletion of brain DA can disrupt performance on avoidance tasks, and stressful stimuli also can increase accumbens DA release. Taking all these data into account, it is not clear that DA in any brain region has some selective role in mediating the effects of rewarding stimuli. For this reason, it is important to provide a detailed characterization of the role of accumbens, striatal and amygdala DA in appetitive and aversive instrumental behavior. The first proposed experiment is designed to study the effects of administration of the DA antagonist haloperidol on lever pressing for food and lever pressing to avoid shook. For this experiment, haloperidol will be administered directly into the nucleus accumbens, striatum and amygdala via chronic indwelling cannulae. In the second experiment, dialysis perfusion methods will be used to study the changes in DA release in nucleus accumbens, striatum and amygdala that are produced by lever pressing for food and lever pressing to avoid shock. The results of these experiments will indicate if DA in these brain regions has a selective involvement in appetitive motivation, or if DA is involved in behavioral processes that are related to stressful as well as rewarding conditions.